No issues with shimming Yokes Frank, If I recall correctly Ducati even do a shim kit for either a 58mm or 56mm down to 53mm. I think I still have some yoke shims somewhere. And the TenKate WP WSBk front end Dallas has for his Pierobon is shimmed. Just don't use to soft a material that will spread, so no copper, or pure aluminium sheet. Stainless or Titanium would be good to use, mine are machined from either alloy bar or tube, but no idea what grade